Spiking food prices have made headlines around the world this year, from eggs in the US to vegetables in India.
The UN Food and Agriculture Organization’s Food Price Index has been slowly increasing over the past six months following declines over much of 2023.
For example, the price of orange juice concentrate in the US was 42% higher in April than it was a year ago, while the price of fresh orange juice in the UK has risen 25% over the last year.
In Greece, the price of olive oil rose by nearly 30% over 2023 and by more than 63% in April of this year.
No single factor alone can explain the rising prices.
But geopolitical conflict, extreme weather events, high input costs and increased demand are all playing a role.
The FAO’s recent Food Outlook report finds that, despite positive forecasts, “global food production systems remain vulnerable to shocks stemming from extreme weather events, geopolitical tensions, policy changes and developments in other markets”.
Carbon Brief has asked a range of scientists and policy experts from around the world what they think are the biggest factors driving spiking global food prices.
These are their responses, first as sample quotes, then, below, in full:
- Prof Elizabeth Robinson: “Whilst one can argue that food crises are not primarily caused by climate or weather, often food price spikes are due to a combination of weather and non-weather related factors.”
- Levi Sucre: “The overexploitation of agricultural lands and the intensive use of agrochemicals have led to a growing need for fertilisers to maintain production, which further increases production costs.”
- Dr Álvaro Lario: “Most food commodity markets present a stable outlook for 2024-25, which should help contain prices for consumers. However…many factors can tip the delicate demand-supply balance.”
- Siraj Hussain: “For long-term and stable food security, the yield has to go up and food losses have to come down.”
- Prof Andrew Challinor: “Put plainly, climate change is beginning to outpace us because it is interacting with our complex interrelated economic and food systems.”
- Dr Rob Vos: “Food prices in global markets are most sensitive to weather conditions and supply disruptions in major producing countries.”
- Prof Alan Matthews: “The rapid recovery of consumer demand following the disruptions caused by the measures to contain the Covid-19 pandemic, extreme weather events, animal disease outbreaks and tight global markets all contributed.”
- Xiomara Paredes: “In short, every time a new regulation is created, it increases production costs, makes market access difficult and thus makes food products more expensive.”
- Dr Manuel Otero: “Food prices have experienced significant increases due to various interrelated economic, social, environmental and political causes.”
- Dr Shouro Dasgupta: “Conflicts are one of the main reasons behind price shocks…Many of these events have also disrupted supply chains and infrastructure.”
Prof Elizabeth Robinson
Director, Grantham Research Institute on Climate Change and the Environment.
London School of Economics and Political Science
Back in 2008, broad underinvestment in the agriculture sector, increasing demand for biofuels, changing diets and speculation – encouraged by declining global food stocks – were already putting longer-term upward pressure on food prices.
The 2008 food crisis was triggered by sequential poor wheat harvests in Australia, a breadbasket country. However, the extreme spike in wheat and rice prices was driven by a combination of export restrictions, panic buying and increased speculation, which amplified the short-term harvest shocks and the longer-term pressures.
More recently, the changing climate, the Covid-19 pandemic and Russia’s invasion of Ukraine have disrupted food production and globally integrated food supply chains, putting rapid upwards pressure on food prices. Whilst one can argue that food crises are not primarily caused by climate or weather, often food price spikes are due to a combination of weather and non-weather related factors.
Earlier this year cocoa prices rapidly increased, a consequence of extreme weather conditions, linked in part to El Niño, resulting in multiple poor harvest seasons in west Africa, combined with longer-term pressures, including disease and ageing cocoa trees, and short-term pressures, particularly speculation, exacerbating the situation further.
Given the changing climate, and in particular increasing extremes of heat and precipitation, food price spikes are likely to be an increasingly common feature of our highly integrated global food systems, in which shocks in one part of the world can relatively easily be amplified and transmitted around the globe.
Levi Sucre
Coordinator
Mesoamerican Alliance of Peoples and Forests
There are several factors causing the increase in food prices worldwide.
Firstly, the high dependency on oil, whose price keeps rising, drives up the costs of food production and transportation. Agricultural machinery, fertilisers and product transportation rely heavily on oil, so any increase in its price directly affects the final cost of food.
Additionally, the overexploitation of agricultural lands and the intensive use of agrochemicals have led to a growing need for fertilisers to maintain production, which further increases production costs.
Monocultures are also degrading the soil, reducing its capacity to produce food sustainably. The lack of crop rotation depletes soil nutrients, diminishing its fertility and forcing farmers to use more fertilisers and pesticides. This not only increases costs but also has negative effects on the environment and health.
The effects of climate change are impacting agricultural production; for example, rising temperatures are disrupting previously predictable agricultural seasons, making crop production more difficult. High temperatures in Mesoamerica continue to destroy crops and reduce food reserves, worsening shortages and driving up prices, affecting nearly 8 million people in El Salvador, Guatemala, Honduras and Nicaragua.
Furthermore, economic injustice, inequality and lack of equity exacerbate the situation. The people with the least resources are the most affected by rising food prices, putting their food security at risk. On the other hand, small-scale producers, who do not use harmful soil practices, do not receive the necessary support to increase their production. These farmers cannot compete with large companies that dominate the market with their monocultures.
Dr Álvaro Lario
President
International Fund for Agricultural Development
International food prices have declined since their historic peak after the start of the war in Ukraine. According to the recently released biennial FAO Food Outlook, most food commodity markets present a stable outlook for 2024-25, which should help contain prices for consumers. But as the report reminds us, many factors can tip the delicate demand-supply balance, impacting food prices and global food security.
The drop in global food prices does not automatically mean that prices have decreased in real terms in local markets, especially considering the strong depreciation of local currencies in most low- and middle-income countries against a robust US dollar.
This is also true for rural communities in these countries, where 80% of the world’s poorest live. In these areas, people can spend up to 70% of their income on food, leaving them with no capacity to absorb any price hikes and pushing them into poverty and hunger. Since Covid-19 emerged, we have seen multiple crises, such as climate change, conflict and record-high food prices, have compounded to push 122 million more people into hunger.
And, despite the current trend, we must remember how fragile our food systems are. They are increasingly threatened by more frequent and intense weather extremes, and volatile geopolitics. Our food systems are overly concentrated on a few crops, countries and producers, and are inefficient, with significant food losses along the value chain and high levels of food waste at the consumer level.
Siraj Hussain
India’s former agricultural secretary. Trustee.
World Food Programme Trust for India
Food inflation has been a source of major concern for a vast majority of Indians.
It is quite an enigma that even cereals, in which India is surplus, have seen double-digit inflation in the last year. Despite the erratic monsoon in 2023, India produced 137m tonnes of rice. Yet in every month since April 2023, the consumer price index inflation for rice was 11-13%.
In the case of wheat, inflation was more than 12% from April to July 2023. The Indian government released 10m tonnes of wheat under an open market sales scheme to cool down wheat prices and the intervention was quite successful as inflation has come down to about 3-7% since July 2023.
The reasons behind inflation in basic cereals of wheat and rice are not well understood. Despite low monsoon rains in 2023-24 due to El Niño, the production of both was not too low in 2023-24. As per the Indian government, wheat production was 113m tonnes.
The real concern in the basket of food inflation comes from vegetables, where inflation in the last year has reached more than 25%. This is attributed to losses in the supply chain from harvesting to marketing. India’s food surpluses are quite small except for rice and sugar. For long-term and stable food security, the yield has to go up and food losses have to come down.
Prof Andy Challinor
Professor of Climate Impacts.
University of Leeds
Every five years, the UK is mandated to report on climate change risks. The scientific evidence for the second of these reports was published in 2017. It highlighted risks from weather-related shocks to international food production and trade as a key risk.
The final report, which is the responsibility of the government, not scientists, endorsed all the conclusions of the evidence report “with the exception of some of those on food security”. The reason? It said: “The government takes a more optimistic view of the levels of resilience that are achieved through functioning markets and diverse sources of supply.”
In the same month that the government response was written, reports of a UK courgette deficit, resulting from climate extremes abroad, soon deepened into wider concerns across a range of vegetables and rationing was commonplace across supermarkets. The World Economic Forum’s 2017 report on global risks identified extreme weather events – already ranked as the most likely global risk in every WEF report since 2014 – as both the most likely and most impactful risk, after weapons of mass destruction.
Skip forward to 2022, when the evidence for the new UK assessment was published. Amongst other additions, an increased underlying vulnerability to climate risk was identified along with a new specific risk of “risk amplification from the interactions and cascades of named risks across systems and geographies”.
The way we as a society (consumers, citizens, government, businesses) choose to set up our food systems has huge implications for stability and resilience – or lack thereof. The 2022 report makes clear that the UK is struggling to keep pace with climate change impacts because of both the pace of change and the way in which the many potential risks to food systems interact with each other.
Put plainly, climate change is beginning to outpace us because it is interacting with our complex interrelated economic and food systems. Until we find ourselves able to look at the big picture and adjust accordingly, we can expect more of the same.
Dr Rob Vos
Director for Markets, Trade and Institutions.
International Food Policy Research Institute
The war in Ukraine caused world market prices for staple foods, especially wheat and vegetable oils, to skyrocket in the first half of 2022. Since then, however, those world market prices have come down to pre-war levels.
At the same time, consumers around the world have felt soaring domestic food price inflation well into 2023. People in some low- and middle-income countries, such as in Argentina, Egypt, Ethiopia, Gaza, Haiti, Sudan, Ukraine and Venezuela, are still seeing the cost of their daily bread and meals going up at high rates today.
What is driving these price fluctuations in global food markets and why are consumer prices not following the same pattern?
Food prices in global markets are most sensitive to weather conditions and supply disruptions in major producing countries. For instance, floods in India caused by the El Niño phenomenon disrupted rice production in India during 2023, pushing up rice prices worldwide.
The war in Ukraine caused shortages in global wheat, maize, sunflower seeds and fertiliser supplies as both Russia and Ukraine are major producers, pushing up wheat, vegetable oil and fertiliser prices.
I should add that the Ukraine war was not the only factor and, in fact, just exacerbated the surge in international food and fertiliser prices induced by the global economic recovery from the Covid-19 recession and the supply chain disruptions (recall the containership pile-up at harbours) that sent oil prices and shipping costs soaring and increasing the cost of farming and food trade worldwide.
Global market prices are further sensitive to misguided policy responses. Governments often respond to expected food supply shortages and price surges by imposing restrictions on exports (such as India’s bans on rice exports in 2023) or lowering import restrictions (as many rice-importing countries did in 2023). While trying to protect their consumers, these “insulation” measures end up just magnifying the price increase.
Why do domestic food prices not necessarily follow the same pattern?
In fact, most countries are relatively insulated from global price shocks as they rely predominantly on their own food production to feed their populations; typically, only 10-15% or less of food consumption is imported.
Domestic conditions for food production and distribution systems thus matter more than global prices. These conditions vary across countries, but countries with the highest rates of consumer price inflation have seen food systems disrupted by intensified conflict (as in Ethiopia, Gaza, Haiti and Sudan, for instance) and those suffering macroeconomic constraints and weak currencies that have kept both general and food price inflation high (e.g. Argentina, Venezuela, Turkey, and many highly indebted low-income countries).
Prof Alan Matthews
Professor Emeritus of European Agricultural Policy
University of Dublin Trinity College
Food prices in the EU rose dramatically in 2022 and 2023. EU food prices were 41% higher in May 2023 relative to the price level in 2015, while the overall price level rose by just 26% during this period. The monthly annual rate of food price inflation peaked at 19.2% in the EU in March 2023.
Even higher rates were recorded in central and eastern Europe, with Hungary a particular outlier, with food price inflation of 46% in February 2023. Since then, food prices have not fallen, but are now increasing at a rate below the general inflation rate for the first time in two years.
There have been multiple drivers of this food price inflation. The rapid recovery of consumer demand following the disruptions caused by the measures to contain the Covid-19 pandemic, extreme weather events, animal disease outbreaks and tight global markets all contributed.
For Europe, the impact of the Russian invasion of Ukraine has been particularly important. There was a direct impact through the increased price of energy, and thus fertilisers and fuel, given the EU’s dependence on imports particularly of Russian gas, but also an indirect impact through the knock-on effect of higher world market crop prices due to the subsequent curtailment of Ukrainian exports to the world market.
Extreme weather events have contributed to food price increases. High temperatures and drought badly affected olive oil production in 2022-23 as well as production of cereals in southern Europe, while heavy rains and wet weather have delayed planting and harvests and damaged fruit quality in northern Europe.
Despite these production losses, a March 2024 study in Communications Earth & Environment estimated that the 2022 extreme summer heat had increased food inflation in Europe by 0.43-0.93 percentage points – so making a relatively minor contribution to the overall 19% increase in food prices at that time. Nonetheless, in more normal times that would cause a more noticeable uptick in food prices, and the authors suggest that the warming projected for 2035 could amplify these numbers by 30-50%.
Xiomara Paredes
Executive Director, Latin American and Caribbean Coordinating Association of Small Fair Trade Producers and Workers
The new regulations that the EU has recently implemented, such as the deforestation-free regulation, changes in organic regulation, human rights and environmental due diligence, entail the investment of additional resources, thus raising production costs.
For example, to comply with the deforestation-free regulation, producers must first invest in geolocation equipment and have technical staff who can survey the points or polygons on the plots of each producer member of the organisation. Geolocating all the producers’ plots also takes time and effort that must be diluted in the installed capacity of the producer organisations.
In short, every time a new regulation is created, it increases production costs, makes market access difficult and thus makes food products more expensive.
Dr Shouro Dasgupta
Environmental Economist
Fondazione CMCC
Visiting Senior Fellow
Grantham Research Institute, LSE
The issue of increasing food prices is multifaceted and is due to a complex set of reasons including conflicts, climate change and supply chain disruptions.
Conflicts are one of the main reasons behind price shocks. For instance, Russia’s invasion of Ukraine, known as the breadbasket of Europe, has substantially reduced exports of wheat, maize and sunflower, resulting in food price fluctuations. While global food prices have decreased from their peak levels at the onset of the conflict, they remain higher than the pre-conflict levels.
Climate change, manifested by increasing temperatures and the increasing intensity and frequency of extreme events such as heatwaves, droughts and floods, has led to crop failures and reduced yields in many parts of the world. This, in turn, has pushed up food prices through supply shocks.
Many of these events have also disrupted supply chains and infrastructure, such as roads, and lowered water levels of major rivers such as the Rhine. Whether due to conflicts or climate change, several countries have imposed export bans on major agricultural commodities (for example, India, Myanmar and Russia on rice; Thailand on sugar; Argentina on beef). These restrictions affect countries that are highly dependent on imports the most.
Several policy failures in the global food system also contribute to food inflation. One such issue is the inadequacy of storage facilities, especially in low- and middle-income countries. Another is the concentration of food production in certain regions and on selected crops (60% of the plant-based calorie intake is provided by rice, wheat and maize) and the fact that global food chains are dominated by a small number of multinational corporations.
Dr Manuel Otero
Director-general, Inter-American Institute for Cooperation on Agriculture
In recent years, food prices have experienced significant increases due to various interrelated economic, social, environmental and political causes. Armed conflicts have disrupted supply chains and food production and distribution, exacerbating shortages and driving up prices. These conflicts have also displaced millions of people, affecting their ability to produce and access food.
Economic shocks, such as the Covid-19 pandemic and its repercussions, plus the slowdown of economies, have reduced consumers’ purchasing power, decreasing incomes and increasing unemployment, which has raised relative demand and prices.
Extreme weather events, such as droughts and storms, have affected agricultural production, reducing supply and increasing production costs, resulting in higher prices for consumers. Volatility in fertiliser markets, driven by trade restrictions and armed conflict, has also increased agricultural production costs, reflected in higher prices for food products.
Trade restrictions, such as export bans, have exacerbated the global food crisis, limiting international food trade and further driving up prices in global markets. According to our Observatory of Public Policies for Agrifood Systems tool, since the pandemic, food inflation has reached 28% annually on a global average – compared to a general inflation of 19% annually.
This is despite the fact that international food prices fell 9% annually for the same comparison period, suggesting that other economic, political and environmental factors contribute to food inflation.
Latin America and the Caribbean is home to 16 net-exporting and 16 net-food-importing countries, so the region has benefited from the increase in international food prices, but has also been one of the most affected by food insecurity due to factors such as increasing poverty.
The post Experts: What is causing food prices to spike around the world? appeared first on Carbon Brief.
Experts: What is causing food prices to spike around the world?
Human-caused greenhouse gas (GHG) emissions in 2024 continued to drive global warming to record levels.
This is the stark picture that emerges in the third edition of the “Indicators of Global Climate Change” (IGCC) report, published in Earth System Science Data.
IGCC tracks changes in the climate system between Intergovernmental Panel on Climate Change (IPCC) science reports.
In doing so, the IGCC fills the gap between the IPCC’s sixth assessment (AR6) in 2021 and the seventh assessment, expected in 2028.
Following IPCC methods, this year’s assessment brings together a team of over 60 international scientists, including former IPCC authors and curators of vital global datasets.
As in previous years, it is accompanied by a user-friendly data dashboard focusing on the main policy-relevant climate indicators, including GHG emissions, human-caused warming, the rate of temperature change and the remaining global carbon budget.
Below, we explain this year’s findings, highlighting the role that humans are playing in some of the fundamental changes the global climate has seen in recent years.
(For previous IGCC reports, see Carbon Brief’s detailed coverage in 2023 and 2024.)
An ‘unexceptional’ record high
Last year likely saw global average surface temperatures hit at least 1.5C above pre-industrial levels. This aligns with other major assessments of the Earth’s climate.
Our best estimate is a rise of 1.52C (with a range of 1.39-1.65C), of which human activity contributed around 1.36C. The rest is the result of natural variability in the climate system, which also plays a role in shaping global temperatures from one year to the next.
Our estimate of 1.52C differs slightly from the 1.55C given by the World Meteorological Organisation (WMO) state of the global climate 2024 report, published earlier this year. This is because they make slightly different selections on which of the available global land and ocean temperature datasets to include. (The warming estimate has varied by similar amounts in past years and future work will aim to harmonise the approaches.)
The height of 2024’s temperatures, while unprecedented in at least the last 2,000 years, is not surprising. Given the high level of human-induced warming, we might currently expect to see annual temperatures above 1.5C on average one year in six.
However, with 2024 following an El Niño year, waters in the North Atlantic were warmer than average. These conditions raise this likelihood to an expectation that 1.5C is surpassed every other year.
From now on, we should regard 2024’s observed temperatures as unexceptional. Temperature records will continue to be broken as human-caused temperature rise also increases.
Longer-term temperature change
Despite observed global temperatures likely rising by more than 1.5C in 2024, this does not equate to a breach of the Paris Agreement’s temperature goal, which refers to long-term temperature change caused by human activity.
IGCC also looks at how temperatures are changing over the most recent decade, in line with IPCC assessments.
Over 2015-24, global average temperatures were 1.24C higher than pre-industrial levels. Of this, 1.22C was caused by human activity. So, essentially, all the global warming seen over the past decade was caused by humans.
Observed global average temperatures over 2015-24 were also 0.31C warmer than the previous decade (2005-14). This is unsurprising given the high rates of human-caused warming over the same period, reaching a best estimate of 0.27C per decade.
This rate of warming is large and unprecedented. Over land, where people live, temperatures are rising even faster than the global average, leading to record extreme temperatures.
But every fraction of a degree matters, increasing climate impacts and loss and damage that is already affecting billions of people.
Driven by emissions
Undoubtedly, these changes are being caused by GHG emissions remaining at an all-time high.
Over the last decade, human activities have released, on average, the equivalent of around 53bn tonnes of CO2 into the atmosphere each year. (The figure of 53bn tonnes expresses the total warming effect of CO2 and other greenhouse gases, such as methane and nitrous oxide, using CO2 as a reference point.)
Emissions have shown no sign of the peak by 2025 and rapid decline to net-zero required to limit global warming to 1.5C with no or limited “overshoot”.
Most of these emissions were from fossil fuels and industry. There are signs that energy use and emissions are rising due to air conditioning use during summer heatwaves. Last year also saw high levels of emissions from tropical deforestation due to forest fires, partly related to dry conditions caused by El Niño.
Notably, emissions from international aviation – the sector with the steepest drop in emissions during the Covid-19 pandemic – returned to pre-pandemic levels.
The amount of CO2 in the atmosphere, alongside the other major GHGs of methane (CH4) and nitrous oxide (N2O), is continuing to build up to record levels. Their concentrations have increased by 3.1, 3.4 and 1.7%, respectively, since the 2019 values reported in the last IPCC assessment.
At the same time, aerosol emissions, which have a cooling effect, are continuing to fall as a result of important efforts to tackle air pollution. This is currently adding to the rate of GHG warming.
Notably, cutting CH4 emissions, which are also short-lived in the atmosphere, could offset this rise. But, again, there is no real sign of a fall – despite major initiatives such as the Global Methane Pledge.
The effect of all human drivers of climate change on the Earth’s energy balance is measured as “radiative forcing”. Our estimate of this radiative forcing in 2024 is 2.97 Watts per square metre (W/m2), 9% above the value recorded in 2019 that was quoted in the last IPCC assessment.
This is shown in the figure below, which illustrates the percentage change in an array of climate indicators since the data update given in the last IPCC climate science report.
Continued emissions and rising temperatures are meanwhile rapidly eating into the remaining carbon budget, the total amount of CO2 that can be emitted if global warming is to be kept below 1.5C.
Our central estimate of the remaining carbon budget from the start of 2025 is 130bn tonnes of CO2.
This has fallen by almost three-quarters since the start of 2020. It would be exhausted in a little more than three years of global emissions, at current levels.
However, given the uncertainties involved in calculating the remaining carbon budget, the actual value could lie between 30 and 320bn tonnes, meaning that it could also be exhausted sooner – or later than expected.
Beyond global temperatures
Our assessment also shows how surplus heat is accumulating in the Earth’s system at an accelerating rate, becoming increasingly out of balance and driving changes around the world.
The data and their changes are displayed on a dedicated Climate Change Tracker platform, shown below.
The radiative forcing of 2.97 W/m2 adds heat to the climate system. As the world warms in response, much of this excess heat radiates to space, until a new balance is restored. The residual level of heating is termed the Earth’s “energy imbalance” and is an indication of how far out of balance the climate system is and the warming still to come.
This residual rate of heat entering the Earth system has now approximately doubled from levels seen in the 1970s and 1980s, to around 1W/m2 on average during the period 2012-24.
Although the ocean is storing an estimated 91% of this excess heat, mitigating some of the warming we would otherwise see at the Earth’s surface, it brings other impacts, including sea level rise and marine heatwaves.
Global average sea level rise, from both the melting of ice sheets and thermal expansion due to deep ocean warming, is included in the IGCC assessment for the first time.
We find that it has increased by around 26mm over the last six years (2019-24), more than double the long-term rate. This is the indicator that shows the clearest evidence of an acceleration.
Sea level rise is making storm surges more damaging and causing more coastal erosion, having the greatest impact on low-lying coastal areas. The 2019 IPCC special report on the oceans and cryosphere estimated that more than one billion people would be living in such low-lying coastal zones by 2050.
Multiple indicators
Overall, our indicators provide multiple lines of evidence all pointing in the same direction to provide a clear and consistent – but unsurprising and worsening – picture of the climate system.
It is also now inevitable that global temperatures will reach 1.5C of long-term warming in the next few years unless society takes drastic, transformative action – both in cutting GHG emissions and stopping deforestation.
Every year of delay brings reaching 1.5C – or even higher temperatures – closer.
This year, countries are unveiling new “nationally determined contributions” (NDCs), the national climate commitments aimed at collectively reducing GHG emissions and tackling climate change in line with the Paris Agreement.
While the plans put forward so far represent a step in the right direction, they still fall far short of what is needed to significantly reduce, let alone stop, the rate of warming.
At the same time, evidence-based decision-making relies on international expertise, collaboration and global datasets.
Our annual update relies on data from NASA and the National Oceanic and Atmospheric Administration (NOAA) and input from many of their highly respected scientists. It is this type of collaboration that allows scientists to generate well-calibrated global datasets that can be used to produce trusted data on changes in the Earth system.
It would not be possible to maintain the consistent long-term datasets employed in our study if their work is interrupted.
At a time when the planet is changing at the fastest rate since records began, we are at risk of failing to track key indicators – such as greenhouse gas concentrations or deep ocean temperatures – and losing core expertise that is vital for understanding the data.
The post Guest post: Why 2024’s global temperatures were unprecedented, but not surprising appeared first on Carbon Brief.
Guest post: Why 2024’s global temperatures were unprecedented, but not surprising
Climate Change
Guest post: How the world’s rivers are releasing billions of tonnes of ‘ancient’ carbon
The perception of how the land surface releases carbon dioxide (CO2) typically conjures up images of large-scale deforestation or farmers churning up the soil.
However, there is an intriguing – and underappreciated – role played by the world’s rivers.
Right now, plants and soils absorb about one-third of the CO2 released by human activity, similar to how much the oceans take up.
Over thousands to millions of years, some of this land-fixed carbon can end up being buried in sediments, where it eventually forms rocks.
The waters that feed rivers flow through plants, soils and rocks in landscapes, picking up and releasing carbon as they go.
This process is generally considered to be a sideways “leakage” of the carbon that is being taken up by recent plant growth.
However, the age of this carbon – how long it resided in plants and soils before it made it into rivers and then to the atmosphere – has remained a mystery.
If the carbon being released by rivers is young, then it can be considered a component of relatively quick carbon cycling.
However, if the carbon is old, then it is coming from landscape carbon stores that we thought were stable – and, therefore, represents a way these old carbon stores can be destabilised.
In our new study, published in Nature, we show that almost 60% of the carbon being released to the atmosphere by rivers is from these older sources.
In total, this means the world’s rivers emit more than 7bn tonnes of CO2 to the atmosphere each year – more than the annual fossil-fuel emissions from North America.
This means that there is a significant leak of carbon from old stores that we thought were safely locked away.
Previous work has shown that local land-use change, such as deforestation and climate-driven permafrost thaw, will directly release old carbon into rivers. Whether this is happening at the global scale remains a significant unknown for now.
Who are you calling old?
How do you tell how old carbon is? We employ the same technique that is used to determine the age of an archaeological relic or to verify the age of a vintage wine – that is, radiocarbon dating.
Radiocarbon is the radioactive isotope of carbon, which decays at a known rate. This enables us to determine the age of carbon-based materials dating back to a maximum age of about 60,000 years old.
We know that some of the carbon that rivers release is very young, a product of recent CO2 uptake by plants.
We also know that rivers can receive carbon from much older sources, such as the decomposition of deep soils by microbes and soil organisms or the weathering and erosion of ancient carbon in rocks.
Soil decomposition can release carbon ranging from a few years to tens of thousands of years. An example of very old soil carbon release is from thawing permafrost.
Rock weathering and erosion releases carbon that is millions of years old. This is sometimes referred to as “radiocarbon-dead” because it is so old all the radiocarbon has decayed.
Rivers are emitting old carbon
In our new study, we compile new and existing radiocarbon dates of the CO2 emissions from around 700 stretches of river around the world.
We find that almost 60% of the carbon being released to the atmosphere by rivers is from older sources (hundreds to thousands of years old, or older), such as old soil and ancient rock carbon.
In the figure below, we suggest how different processes taking place within a landscape can release carbon of different ages into rivers, driving its direct emission to the atmosphere.
So, while rivers are leaking some modern carbon from plants and soils as part of the landscape processes that remove CO2 from the atmosphere, rivers are also leaking carbon from much older landscape carbon stores.
One major implication of this finding is that modern plants and soils are leaking less carbon back to the atmosphere than previously thought, making them more important for mitigating human-caused climate change.
We find that the proportion of old carbon contributing to river emissions varies across different ecosystems and the underlying geology of the landscapes they drain.
In the figure below, we show that landscapes underlain by sedimentary rocks, which are the most likely to contain substantial ancient (or “petrogenic”) carbon, also had the oldest river emissions. We also show that the type of ecosystem (biome) was also important, although the patterns were less clear.
What is obvious is that at least some old carbon was common across most of the rivers we observed, regardless of size and location.
We provide evidence that there is a geological control on river emissions. And the variability in the ecosystem also indicates important controlling factors, such as soil characteristics, vegetation type and climate – especially rainfall patterns and temperature which are known to impact the rate of carbon release from soils and rock weathering.
Are old carbon stores stable?
Long-term carbon storage in soils and rocks is an important process regulating global climate.
For example, the UK’s peatlands are important for regulating climate because they can store carbon for thousands of years. That is why restoring peatlands is such a great climate solution.
Rivers emit more than 7bn tonnes of CO2 to the atmosphere each year – that’s equivalent to about 10-20% of the global emissions from fossil fuel burning annually.
If 60% of river carbon emissions are coming from old carbon stores, then this constitutes a significant leak of carbon from old stores we thought were safely locked away.
Another major implication of our study is that these old carbon stores can be mobilised and routed directly to the atmosphere by rivers, which would exacerbate climate change if these stores are further destabilised.
As can be seen in the figure below, we found that river carbon emissions appeared to be getting older since measurements first began in the 1990s (lower F14Catm means older radiocarbon ages).
We found that river carbon emissions appeared to be getting older since measurements first began in the 1990s.
While there are several caveats to interpreting this trend, it is a warning sign that human activities, especially climate change, could intensify the release of carbon to the atmosphere via rivers.
Given the strong link between soil carbon and river emissions, if this trend is a sign of human activity disturbing the global carbon cycle, it is likely due to landscape disturbance mobilising soil carbon.
Using rivers to monitor global soil carbon storage
Rivers collect waters from across the landscapes they flow through and therefore provide a tool to track processes happening out of sight.
A drop of water landing in a landscape travels through soils and rock before reaching the river, and its chemistry, including its radiocarbon age, reflects the processes occurring within the landscape.
Monitoring the age of carbon in rivers can therefore tell you a lot about whether their landscapes are storing or releasing carbon.
This has been shown to help identify carbon loss in degraded tropical peatlands, thawing Arctic permafrost and due to deforestation.
River radiocarbon is sensitive to environmental change and could therefore be a powerful monitoring tool for detecting the onset of climate tipping points or the success of landscape restoration projects, for example.
While we present data spread out across the world, there are quite a few gaps for important regions, notably where glacier change is happening and others where droughts and flood frequencies are changing.
These include areas with low amounts of data in Greenland, the African continent, the Arctic and Boreal zones, the Middle East, eastern Europe, western Russia, Central Asia, Australasia and South America outside of the Amazon.
All these regions have the potential to store carbon in the long-term and we do not yet know if these carbon stores are stable or not under present and future climate change.
River radiocarbon offers a powerful method to keep tabs on the health of global ecosystems both now and into the future.
The post Guest post: How the world’s rivers are releasing billions of tonnes of ‘ancient’ carbon appeared first on Carbon Brief.
Guest post: How the world’s rivers are releasing billions of tonnes of ‘ancient’ carbon
Climate Change
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A National Quest for Uranium Comes to Remote Western Alaska, Raising Fears in a Nearby Village
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